1-For the cvs sparks work, pactch fightx.sff and
  fightx.air files of your mugen

This files come in data folder usually into a folder of your lifebars.

2-Make sure that in the file fight.def of your mugen the scale of fightfx is
  properly calibrated, if the sparks look to big or small increase or
  decrease that number.


Example of calibrated fightx.def

[Files]
sff = fight.sff
snd = fight.snd
font1 = jg.fnt
font2 = num1.fnt
font3 = name1.fnt
fightfx.sff = fightfx.sff
fightfx.air = fightfx.air
common.snd = common.snd

;-------------
[FightFx]
scale = 2   <---------------------this is the scale

;-------------




How modify your chars

change the values of sparkno of all HitDef of your characters for this values:


--------------------------------------------------------------------------------------------
Normal-Hit = 7100+(Random%8)      - Normal-Cut = 7110+(Random%64)

Spesial-Hit = 7200+(Random%8)     - Special-Cut = 7210+(Random%64)

Hyper-Hit = 7300+(Random%8)       - Hyper-Cut = 7310+(Random%64)
--------------------------------------------------------------------------------------------

Normal-Guard = 7000

Special-Guard and Hyper-Guard = 7010

--------------------------------------------------------------------------------------------






Example of how modify the Hitdef of your chasrs


[State 200, 1]
type = HitDef
trigger1 = AnimElem = 3
attr = S, NA                                                                 
damage = 23, 0                                                               
animtype = Light                                                             
guardflag = MA                                                             
hitflag = MAF                                                             
priority = 3, Hit                                                           
pausetime = 8, 8                                                             
sparkno = 7100+(Random%8)        <----------------- Normal-Hit               
guard.sparkno = 7000                   <----------------- Normal-Guard             
sparkxy = -10, -76                                                           
hitsound = 5, 0                                                             
guardsound = 6, 0                                                           
ground.type = High                                                         
ground.slidetime = 5                                                       
ground.hittime  = 11                                                         
ground.velocity = -4                                                         
airguard.velocity = -1.9,-.8                                                 
air.type = High                                                             
air.velocity = -1.4,-3                                                     
air.hittime = 15


This is another example for the explods that needs saprks more common on HitAdd like throds

[State 1000, Spark]
type = Explod
trigger1 = AnimElem = 17
Anim = f7100+(random%8)         <----------------- Normal-Hit 
pos = 96, 0
postype = p1
ownpal = 1
bindtime = -1
pausemovetime = -1
supermove = 1
ignorehitpause = 1
sprpriority = 2
persistent = 0